1. Field of the Invention
The present invention relates to a corneal surgery apparatus for ablating a part of a cornea of a patient""s eye to correct a refractive error of the eye or to remove a lesion therefrom.
2. Description of Related Art
Conventionally known is a corneal surgery apparatus that ablates a corneal stroma of a patient""s eye with an excimer laser or the like to change a refractive power of the eye to correct ametropia including myopia, hypermetropia, astigmatism and the like, or to remove an affected part of the cornea such as opacity. Also known is a corneal shape measurement apparatus (hereinafter referred to as a topography apparatus) that projects a placido ring onto a cornea and photographs an image of the placido ring to measure the corneal surface shape. Further, it has also been suggested to input the corneal shape data obtained by the topography apparatus to a corneal surgery apparatus. An amount to be ablated is calculated from the data and also the post-operative refractive power to be obtained. The ablation is carried out in accordance with the calculated ablation amount.
However, the above-described way presents the following problems. One of the problems lies in the case of measuring a corneal shape of a patient""s eye by a topography apparatus first, and then performing surgery to correct the refractive power by a separate corneal surgery apparatus based on the data captured from the topography apparatus. In this case, the positional relationship between the topography apparatus and the patient""s eye is not necessarily the same as the positional relationship between the corneal surgery apparatus and the patient""s eye. It is especially so, when the measurement by the topography apparatus is carried out with the patient being sit and fixed by the face, while the surgery by the corneal surgery apparatus is carried out with the patient being laid on his back. Due to the inclination of the face, the gravity and other various factors, it is often the case that the patient""s eye is not in a uniform state. This results in the possibility of ablating an unintended part of the cornea. In this case, the post-operative corneal shape may differ from the expected one and the refractive error may not be corrected as expected.
One possible way to address the above problem is to combine the corneal surgery apparatus and the topography apparatus into one apparatus so as to make the topography position and the corneal surgery position coincide with each other relative to the patient""s eye. However, an attempt to make one apparatus by combining the topography apparatus including a placido ring projecting unit and a TV camera for photographing its corneal reflex and the like with the corneal surgery apparatus including a laser irradiation optical system and an observation optical system will results in an undesirably large apparatus.
The present invention has been made in view of the above circumstances and has an object to overcome the above problems and to provide an apparatus for corneal surgery which is small and compact, while being capable of preventing displacement between a corneal shape measurement position and a laser beam irradiation position upon corneal surgery to remove a part of the cornea with a laser.
Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, a corneal surgery apparatus which ablates corneal tissue with a laser beam, the apparatus comprises an irradiation unit including a light directing optical system for directing the laser beam to an intended range on a cornea of a patients s eye, wherein the laser beam has a wavelength in a far ultraxe2x80x94violet region and intensity capable of causing ablation and a corneal shape measurement unit, provided inside the apparatus, for measuring a three-dimensional shape of the cornea, the corneal shape measurement unit including a measurement light projecting optical system for projecting measurement light onto the cornea and its convergent point is shifted by moving a focusing lens along an optical axis, a measurement light receiving optical system including a photo-detector for receiving reflected light from the cornea and its convergent point is shifted by moving a focusing lens along an optical axis, a scanning unit for shifting a projection spot of the measurement light on the cornea in XY directions and an arithmetic unit for performing arithmetic to obtain the three-dimensional shape of the cornea from a position of the projection spot, a result detected by the photo-detector and a position to which the focusing lens is moved.
As described above according to the present invention, it is possible to prevent the displacement between the corneal shape measurement position and the laser irradiation spot upon corneal laser surgery to remove a portion of the cornea. Simultaneously, it is also possible to make the whole apparatus compact in size. In addition, according to the present invention, the corneal thickness can be measured so that judgement on ablation or adjustment of the ablation amount may be made based on the measured corneal thickness.